perf bench: Add memcpy() benchmark

perf bench: Add memcpy() benchmark

'perf bench mem memcpy' is a benchmark suite for measuring memcpy()
performance.

Example on a Intel(R) Core(TM)2 Duo CPU E6850 @ 3.00GHz:

| % perf bench mem memcpy -l 1GB
| # Running mem/memcpy benchmark...
| # Copying 1MB Bytes from 0xb7d98008 to 0xb7e99008 ...
|
|     726.216412 MB/Sec

Signed-off-by: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1258471212-30281-1-git-send-email-mitake@dcl.info.waseda.ac.jp>
[ v2: updated changelog, clarified history of builtin-bench.c ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>